Kernel panic when waking up after screens go to dpms sleep
Submitted by Brad Campbell
Assigned to Default DRI bug account
Created attachment 145332
Multiple instances of the Panic
iMac late 2011 with 2 Thunderbolt displays.
Kernel 5.2 finally got DP routing working to allow both TB displays to work, however I'm now getting lockups which appear to be triggered in radeon_dp_needs_link_train.
I'm capturing these over netconsole as it leaves the machine paralysed.
Attachment faults.txt has 4 separate instances of the fault from 4 different boots.
This machine stays on 24/7 and this seems to occur when the displays wake up after a dpms sleep. Having said that I've also seen the fault when doing something innocuous like changing the audio volume.
Generally at least 2 of the screens wakeup, so I have displays with a lockscreen asking for a password and a mouse, but the machine is dead.
The last example in faults.txt left the machine in a state where I could ssh in and reboot it. All the others required a hard power cycle.
I'm currently using 5.2.11. Previously I was using 4.17, but I can't roll back prior to 5.2 without losing the second TB display, and it can take hours or days to hit so bisection would be difficult.
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Blackcomb [Radeon HD 6970M/6990M] (prog-if 00 [VGA controller])
Subsystem: Apple Inc. Radeon HD 6970M
Flags: bus master, fast devsel, latency 0, IRQ 79
Memory at 90000000 (64-bit, prefetchable) [size=256M]
Memory at a8800000 (64-bit, non-prefetchable) [size=128K]
I/O ports at 2000 [size=256]
Expansion ROM at a8820000 [disabled] [size=128K]
Capabilities:  Power Management version 3
Capabilities:  Express Legacy Endpoint, MSI 00
Capabilities: [a0] MSI: Enable+ Count=1/1 Maskable- 64bit+
Capabilities:  Vendor Specific Information: ID=0001 Rev=1 Len=010 <?>
Capabilities:  Advanced Error Reporting
Kernel driver in use: radeon
Kernel modules: radeon
Attachment 145332, "Multiple instances of the Panic":